In conventional scanning electron microscopes (SEM), the specimen chamber is typically maintained at a vacuum pressure of 0.01 Pa or lower. This allows maintaining a sufficiently low pressure level in the electron gun and also to use so-called “in-lens” or “through-the-lens” detector systems, which are typically disposed inside the particle optical column. These low pressure levels also prevent degradation of the image quality, which may occur due to collisions of primary beam electrons with residue gas particles.
However, the requirement of maintaining the specimen chamber at a high vacuum makes it difficult to inspect wet or non-conductive specimens, such as biological materials, plastics, ceramics, minerals and fibers. Wet specimen deteriorate the vacuum pressure level by outgassing. For non-conductive specimen, the low vacuum pressure level prevents dissipation of surface charges that accumulate on the surface.
To enable inspection of wet or non-conductive specimens, preparation techniques, such as drying, freezing or vacuum coating have been developed. These techniques, however, are often not desirable, since they tend to alter or mask the sample surface.
Attempts to overcome these constraints have led to the development of special kinds of scanning electron microscopes, such as variable-pressure scanning electron microscopes (VPSEMs) and environmental scanning electron microscopes (ESEMs). These types of scanning electron microscopes can be operated at elevated gas or vapor pressure levels in the specimen chamber, which can be up to 2500 Pa in the case of ESEMs. Operation at these elevated pressure levels is made possible by one or more differential pressure apertures, which are provided to limit the amount of gas in the electron optical column.
For detection of secondary electrons and backscattered electrons at elevated pressure levels, gaseous detectors have been developed. However, these detectors have shown major drawbacks. First, gaseous detectors typically produce signals with a low signal to noise ratio. This is particularly disadvantageous if samples are inspected which are sensitive to electron beam irradiation, such as semiconductors, plastics, and biological samples. Further, inspection of sensitive samples typically requires a low energy primary electron beam. Gaseous detectors, however, are unsuitable for use with low energy primary electron beams below 3 keV.
Inspections of objects at high pressure levels also have shown not to be fully compatible with through-the-lens detector systems, since the additional differential pressure apertures often reduce the amount of backscattered electrons and secondary electrons, which pass through the objective lens, and hence, the detected electron intensity. Further, the additional differential pressure apertures typically limit the attainable field of view.
Accordingly, there is a need to provide a particle optical system, which allows efficient inspection of a wide range of objects.
Embodiments provide a charged particle optical apparatus, comprising: a particle optical arrangement configured to define a beam path for a primary particle beam for inspecting an object. The particle optical arrangement may further be configured to generate an objective lens field for focusing the primary particle beam onto the object. The particle optical arrangement may include a first electrode, which is at least partially disposed in a first vacuum zone and which forms a channel. The primary particle beam may pass through at least a portion of the channel. The objective lens field may include a static electric field which is generated by using the first electrode. The charged particle optical apparatus may include a second electrode which surrounds at least a section of the primary particle beam path. The section may extend in the first vacuum zone and downstream of the channel. The charged particle optical apparatus may include a third electrode having a differential pressure aperture. Through the differential pressure aperture, the particle beam path may exit from the first vacuum zone. The charged particle optical apparatus may include a particle detector for detecting emitted particles. The emitted particles may be emitted from the object. The emitted particles may pass through the differential pressure aperture of the third electrode. The particle optical apparatus may be configured so that the first, second and third electrodes are operable at different potentials relative to each other.
Thereby, a particle optical apparatus is provided which allows efficient inspection of objects at elevated pressures levels in the specimen chamber. In particular, the particle optical apparatus generates the electrostatic field in the vicinity of the differential pressure aperture of the third electrode in such a way that the thereby introduced aberrations of the primary beam are small in comparison to the aberrations, which are introduced by the objective lens.
More specifically, it has been shown that as a result of the second electrode, the electrostatic field has a high degree of homogeneity at positions on the optical axis in the vicinity of the axial position of the differential pressure aperture of the third electrode. Furthermore, comparatively low electric field strengths within the differential pressure aperture of the third electrode are obtained.
Detecting emitted particles which have passed through the differential pressure aperture of the third electrode has advantages over using gaseous detectors. Gaseous detectors rely on gaseous amplification in the pressure-controlled interior of the specimen chamber. Gaseous amplification, also denoted as gas cascade amplification, is generated in a gaseous environment, where secondary electrons are accelerated by an electric field and thereby gain sufficient energy for ionizing gas molecules. The ionization of gas molecules produces additional free electrons which are in turn sufficiently accelerated to cause ionization.
Notably, due to the detection of the emitted particles which have passed through the differential pressure aperture, the path length of the primary particle beam in the elevated pressure atmosphere of the specimen chamber can be made very short, even shorter than 500 micrometers. The short path length can be obtained by adjusting the distance between the object and the final differential pressure aperture, through which the primary particle beam enters into the specimen chamber. Such short path lengths, however, are incompatible with gaseous amplification.
The short path length of the primary particle beam in the pressure-controlled interior of the specimen chamber in turn allows inspection of the object at low primary particle energies, such as 1 keV or even lower. Compared thereto, using gaseous detectors below primary particle beam energies of 3 keV typically yield images of unsatisfactory signal to noise ratio as a result of scattering of primary particles.
Hence, the charged particle optical apparatus allows inspection of objects which are sensitive to irradiation by the primary particle beam, which requires low primary particle energies. Inspection of these sensitive objects is further facilitated in that detector systems can be used, which do not rely on gaseous amplification and thereby have a high signal to noise ratio, compared to gaseous detectors. This in turn allows using low primary particle beam intensities.
The charged particle optical apparatus may be a particle microscope, in particular a scanning particle microscope. The scanning particle microscope may be a scanning electron microscope and/or a focused ion beam microscope. The focused ion beam microscope may comprise a gas field ion source, a plasma ion source and/or a liquid metal ion source. By way of example, the focused ion beam microscope is a noble gas ion microscope, in particular a helium ion microscope.
The particle optical arrangement may be configured to focus the primary particle beam on a surface of the object. The particle optical arrangement may include a deflector system which is configured to deflect the primary particle beam in order to scan the primary particle beam across the object surface. The particle optical arrangement may include further components such as a condenser lens and/or a particle gun.
The objective lens field may include an electrostatic field and/or a magnetostatic field. The electrostatic field may be generated by using the first electrode, in particular an object-side end portion of the first electrode, and/or the second electrode. The electrostatic field may further be generated by using one or more further electrostatic field generating electrodes. These one or more further electrostatic field generating electrodes may include one or more magnetic pole pieces. The objective lens field may be configured to focus a section of the primary particle beam which enters into the objective lens field to a spot on the object surface. The spot may be configured so that 50% of the beam intensity of the spot is located within a circle having a diameter of less than 20 nanometers, less than 15 nanometers, or less than 5 nanometers.
The first electrode forms a channel, wherein the primary particle beam path passes through at least a portion of the channel. The first electrode may be non-magnetic. The first electrode may be configured as a liner electrode and/or a beam booster. The first electrode may represent an innermost wall for the primary particle beam path at locations, where the primary particle beam path extends within the channel. The object-side end portion of the first electrode may include an exit aperture through which the primary particle beam exits from the channel. Through the exit aperture, the emitted particles may enter into the channel. The particle detector may be disposed at least partially inside the channel.
The particle optical arrangement is configured so that a potential of the first electrode relative to the second electrode can be adjusted to values greater than +1 kV or greater than +2 kV or greater than +5 kV or greater than +10 kV. The potential may be less than +50 kV or less than +20 kV.
Emitted particles, which are emitted from the object, pass through the differential pressure aperture of the third electrode. The emitted particles may be emitted in response to irradiation with the primary particle beam.
The emitted particles may be primary particles, which are scattered by the object and/or secondary particles, which are emitted from the object in response to irradiation with the primary particles. If the charged particle optical apparatus is configured as a scanning electron microscope, the primary particles, which are scattered by the object may be backscattered electrons and the secondary particles may be secondary electrons. If the charged particle optical apparatus is configured as a helium ion microscope, the primary particles, which are scattered from the object may be backscattered helium ions and the secondary particles may be secondary electrons and/or secondary ions.
The object-side end portion of the first electrode may be surrounded by a magnetic pole piece of the objective lens. The primary particle beam path may enter the channel of the first electrode at a position upstream of the objective lens field or upstream of a condenser lens field. The condenser lens field may be generated by the particle optical arrangement. The condenser lens field may include a magnetostatic field and/or an electrostatic field.
One or more or each of the differential pressure apertures described herein may be defined as an aperture, which is disposed between two vacuum zones and/or which connects two vacuum zones. A differential pressure drop may be maintainable across the differential pressure aperture. Each of the vacuum zones described herein may have a uniform or substantially uniform pressure level. For each of the differential pressure apertures, a pressure ratio P2/P1 across the differential pressure aperture may be below 0.5, or below 0.1, or below 0.01, or below 0.001. P1 and P2 are the pressure levels of the vacuum zones, between which the differential pressure aperture is disposed.
At least one, or all, of the vacuum zones of the particle optical arrangement may include a vacuum port for evacuating the respective vacuum zone. The vacuum ports may be in fluid communication with a vacuum source. The vacuum source may include a vacuum pump. The vacuum port may be connected to the vacuum source via a vacuum line.
A diameter of the differential pressure aperture of the third electrode may be greater than 400 micrometers, or greater than 800 micrometers. The diameter may be smaller than 3000 micrometers, or smaller than 2500 micrometers. If the aperture is non-circular, the diameter may be a largest diameter measured at the differential pressure aperture. The diameter may be measured in a direction perpendicular to an optical axis of the particle optical arrangement. At least a portion of the third electrode may be in the form of a tapered tube. The tapered tube may taper towards the object or may taper away from the object. At least a portion of an inner peripheral surface and/or at least a portion of an outer peripheral surface of the third electrode may have a tapered shape and/or a frustoconical shape. The tapered shape and/or the frustoconical shape may taper towards the object or may taper away from the object.
The third electrode may include an edge which surrounds the differential pressure aperture. The edge may have a thickness of less than 300 micrometers or less than 50 micrometers. The thickness may be greater than 0.4 micrometers. At least a portion of the third electrode may form at least a portion of a detector. By way of example, at least a portion of the third electrode may form a collector electrode. The collector electrode may be part of a gaseous particle detector and/or may be configured to collect electrons without gaseous amplification.
After the primary particles have exited from the channel, the primary particles may move along a section of the primary particle beam path, which is surrounded by the second electrode. In other words, the section extends downstream of the channel. At least a portion of the second electrode may be disposed in the first vacuum zone. The second electrode may include a surface portion, which is an innermost wall for at least a portion of the section of the primary particle beam path. The surface portion may form an opening, a constriction and/or an innermost edge of an inward extending rim. The second electrode may form an opening through which the primary particle beam path passes. The opening may be a pressure communication aperture. In other words, the opening does not form a differential pressure aperture.
The differential pressure aperture of the third electrode may be disposed downstream of the second electrode relative to the primary particle beam path. The differential pressure aperture of the third electrode may be disposed downstream of a final magnetic pole piece of the objective lens, as seen along the primary particle beam path.
The charged particle optical apparatus is configured so that the first, second and third electrodes are operable at different potential levels relative to each other. The potential level of at least two of the first to third electrodes may be variable, in particular controllably variable. At least two of the first to third electrodes may be electrically connected to a voltage source. One of the first to third electrodes, in particular the second electrode, may be electrically connected to ground potential.
The particle detector, which is configured to detect emitted particles which have passed through the differential pressure aperture of the third electrode, may be a through-the-lens particle detector. A through-the-lens particle detector may be defined herein as a detector which is configured to detect emitted particles after the emitted particles have passed through a principal plane of a particle lens of the particle optical arrangement. The particle lens may be at least a portion of the objective lens. Additionally or alternatively, a through-the-lens detector may be defined herein as a detector which is configured to detect emitted particles after the emitted particles have passed a narrowest portion of an opening formed by at least one or all magnetic pole pieces of the objective lens. The particle detector may be disposed in the first vacuum zone or a vacuum one which is disposed upstream of the first vacuum zone relative to the primary particle beam path.
The particle detector may be configured to selectively detect primary particles and/or secondary particles. In particular, the particle detector may be configured to selectively detect backscattered electrons and/or secondary electrons. One or more particle receiving surfaces of the particle detector may be disposed circumferentially around the primary particle beam path.
The charged particle optical apparatus may include a gaseous detector. The gaseous detector may be configured as a collector electrode detector and/or a gas scintillation detector. The collector electrode detector may be configured to collect electrons generated in the gas cascade by means of a detector electrode. The gas scintillation detector may be configured to detect scintillation radiation generated by the gas cascade.
According to an embodiment, in an inspection operation mode of the particle optical apparatus, a potential level of the third electrode is between a potential level of the first electrode and a potential level of the second electrode.
It has been found that thereby, a particularly high degree of field homogeneity on positions on the optical axis in the vicinity of the differential pressure aperture of the third electrode can be obtained. Further this also results in a comparatively low field strength. Thereby, less aberrations are introduced into the primary particle beam. In the inspection operation mode, the potential of the first electrode relative to the second electrode may be positive.
The charged particle optical apparatus may be configured to adjust the potential of the first and/or third electrode depending on one or more operational parameters of the charged particle optical apparatus. These one or more operational parameters may include the pressure level of the pressure-controlled interior of the specimen chamber, the potential of the fourth electrode and/or the potential of the second electrode.
A controlling function of the charged particle optical apparatus for controlling the potential of the third electrode may be activated and/or deactivated depending on a vacuum pressure level in the specimen chamber. In particular, the control function may be activated if the pressure level in the specimen chamber is below a threshold value. The threshold value may be pre-stored and/or pre-determined.
According to an embodiment, in the inspection operation mode, the potential of the third electrode relative to the second electrode has a value of at least +100 V or at least +400 V or at least +600 V. The potential of the third electrode relative to the second electrode may have a value which is less than +3000 V, or less than +1000 V.
In the inspection operation mode, the potential of the first electrode relative to the second electrode may have a value greater than +1 kV, greater than +2 kV or greater than +5 kV or greater than +10 kV. The potential may be less than +50 kV or less than +20 kV.
In the inspection operation mode, the potential level of the second electrode may deviate from the potential of the specimen chamber or may deviate from ground potential by less than plus or minus 500 V, or less than plus or minus 300 V, or less than plus or minus 100 V, or less than plus or minus 50 V, or less than plus or minus 5 V. In the inspection operation mode, the potential of the second electrode may be or may substantially be the potential level of the specimen chamber and/or ground potential.
According to an embodiment, the second electrode and the object-side end portion of the first electrode may form an axial gap, relative to the optical axis of the particle optical arrangement. The axial gap may surround the beam path of the primary particle beam. According to an embodiment, an object-side end face of the end portion of the first electrode may be disposed in opposed relationship to a surface portion of the second electrode. The end face and/or the surface portion may surround the primary particle beam path. The end face and the surface portion may be parallel or substantially parallel relative to each other. The end face and/or the surface portion may be curved, substantially plane or plane.
According to a further embodiment, in the inspection operation mode of the charged particle optical apparatus, the potential of the first electrode relative to the second electrode (V1) divided by the potential of the third electrode relative to the second electrode (V3), i.e. the value V1/V3. is greater than 2 or greater than 3 or greater than 4 or greater than 5.
According to a further embodiment, the second electrode forms a constriction through which the primary particle beam path passes. A position of a narrowest part of the constriction, as measured along an optical axis of the particle optical arrangement, is disposed between the first electrode, or between an object-side end portion of the first electrode, and the differential pressure aperture of the third electrode.
It has been shown that thereby, the third electrode can be shielded from the first electrode. The narrowest part of the constriction may form an opening. The opening may form a pressure communication aperture. In other words, the constriction does not form a differential pressure aperture.
The primary particle beam may pass through the narrowest part of the constriction after exiting from the channel of the first electrode and before passing through the differential pressure aperture of the third electrode.
An inner diameter at the narrowest part of the constriction may be greater than 2 millimeters, or greater than 4 millimeters. The inner diameter may be less than 15 millimeter, or less than 8 millimeters. The inner diameter may be measured perpendicular to the optical axis. If the narrowest part forms a non-circular opening, the inner diameter may be a smallest diameter measured at the narrowest part. The inner diameter may be smaller than an outer diameter of the object-side end portion and/or an object-side end face of the first electrode. The outer diameter may be measured perpendicular to the optical axis. The outer diameter may be a maximum outer diameter of all diameters measured at the object-side end portion and/or the object-side end face. The inner diameter of the narrowest part of the constriction may be smaller or smaller than 90%, or smaller than 80%, or smaller than 70% of the outer diameter.
The constriction may be formed by a rim, which extends inward toward the primary particle beam path. The rim, in particular an inner peripheral surface of the rim may surround the primary particle beam path. The rim and/or the inner peripheral surface may be disposed in the first vacuum zone. An axis of an inner peripheral surface of the rim and/or an axis of the rim may be aligned or substantially aligned with the optical axis of the particle optical arrangement. The inner peripheral surface may have a rounded, chamfered and/or angled profile.
The second electrode, in particular the rim, which is formed by the second electrode, may include a first inward extending surface. The first inward extending surface may surrounds the primary particle beam path. The first inward extending surface may be plane or substantially plane. The first inward extending surface may face the end portion of the first electrode and/or may be averted from the third electrode. The first inward extending surface may be oriented perpendicular or substantially perpendicular to the optical axis of the particle optical arrangement. The first inward extending surface may be parallel or substantially parallel to an object-side end face of the first electrode. The end face may be plane, or substantially plane. The end face may be oriented perpendicular to the optical axis of the particle optical arrangement or substantially oriented perpendicular to the optical axis.
The second electrode, in particular the rim, which is formed by the second electrode, may include a second inward extending surface. The second inward extending surface may surround the primary particle beam path. The second inward extending surface may be plane or substantially plane. The second inward extending surface may face the third electrode and/or may be averted from the object-side end portion of the first electrode. The second inward extending surface may be oriented perpendicular or substantially perpendicular to the optical axis of the particle optical arrangement.
The second electrode, in particular the rim, may include a source-side shoulder. A distance between the source-side shoulder and the differential pressure aperture of the third electrode, as measured along the optical axis of the particle optical arrangement, may be greater than 1.3 millimeters or greater than 2 millimeters. The distance may be smaller than 5 millimeters or smaller than 3.5 millimeters.
According to a further embodiment, the charged particle optical apparatus further comprises a fourth electrode having a differential pressure aperture wherein the differential pressure aperture of the fourth electrode is disposed in the primary particle beam path between the differential pressure aperture of the third electrode and the object.
It has been shown that thereby, a sufficiently low vacuum pressure level can be maintained in the first vacuum zone even at comparatively high pressure levels in the specimen chamber. This allows maintenance of the first electrode at comparatively high voltage levels, thereby permitting a high performance of the objective lens. Moreover, this allows use of particle detectors and/or charged particle energy analyzers in the first vacuum zone which require a comparatively low vacuum level for operation. Furthermore, the comparatively low pressure level in the first vacuum zone also reduces scattering of primary particles.
By way of example, the charged particle optical apparatus, having at least the differential pressure apertures of the third and fourth electrodes, may be configured so that at a vacuum pressure level of 600 Pa in the specimen chamber, the vacuum pressure level in the first vacuum zone is lower than 20 Pa, lower than 10 Pa or lower than 5 Pa, or lower than 1 Pa.
The differential pressure aperture of the fourth electrode may be a final differential pressure aperture through which the primary particle beam path passes. Through the differential pressure aperture of the fourth electrode, the primary particle beam may enter into the pressure-controlled interior of the specimen chamber.
According to a further embodiment, the charged particle optical apparatus includes an intermediate vacuum zone. After exiting from the first vacuum zone, the primary particle beam path may enter into the intermediate vacuum zone. After passing through the intermediate vacuum zone, the primary particle beam path may enter into the pressure-controlled interior of the specimen chamber. The third electrode may be disposed between the first vacuum zone and the intermediate vacuum zone. The fourth electrode may be disposed between the intermediate vacuum zone and the pressure-controlled interior of the specimen chamber. The particle detector may detect emitted particles, which pass through the differential pressure apertures of the third and fourth electrodes.
The intermediate vacuum zone may have a vacuum port for evacuating the intermediate vacuum zone. The vacuum port may be in fluid communication with a vacuum source.
A diameter of the differential pressure aperture of the fourth electrode may have a value smaller than 2000 micrometers or smaller than 500 micrometers. The diameter may be greater than 20 micrometers or greater than 100 micrometers. The diameter may be measured in a direction perpendicular to the optical axis. If the differential pressure aperture is non-circular, the diameter may be a largest diameter measured at the differential pressure aperture.
At least a portion of the fourth electrode may be in the form of a tapered tube. The tapered tube may taper towards the object or tapers away from the object. At least a portion of an inner peripheral surface and/or at least a portion of an outer peripheral surface of the fourth electrode may have a tapered shape or a frustoconical shape. The tapered shape and/or the frustoconical shape may taper toward the object or may taper away from the object.
Through the tapered form of the outer peripheral surface of the fourth electrode, a comparatively large collection solid angle region may be provided for particle and/or radiation detectors, which are mounted in the pressure-controlled interior of the specimen chamber and which are configured to detect particles and/or radiation. Examples for such radiation and/or particle detectors are EDX (energy dispersive X-ray) detectors, WDS (wavelength dispersive spectroscopy) detectors, gas scintillation detectors, collector electrode gaseous detectors, and cathodoluminescence detectors
Furthermore, the tapered form of the outer peripheral surface of the fourth electrode allows placing the object plane of the particle optical arrangement comparatively close to the differential pressure aperture of the fourth electrode. Thereby, the segment of the primary particle beam path which traverses the vacuum zone of the interior of the specimen chamber is comparatively short. This allows efficient use of electron beams with low kinetic energies (even with energies as low as 1 keV), which have a comparatively short mean free path in the interior of the specimen chamber if the interior of the specimen chamber is maintained at an elevated pressure level.
A ratio of the diameter (D2) of the differential pressure aperture of the fourth electrode over a diameter of the differential pressure aperture of the third electrode (D1), i.e. the ratio D2/D1, may have a value smaller than 0.8 or smaller than 0.6. The ratio may be greater than 0.2 or greater than 0.12. Thereby, a large collection efficiency can be obtained even for comparatively high pressure levels in the vacuum chamber.
A distance between the differential pressure aperture of the third electrode and the differential pressure aperture of the fourth electrode, as measured along the optical axis of the particle optical arrangement, may be greater than 3 millimeters or greater than 4 millimeters. The distance may be smaller than 8 millimeters or smaller than 15 millimeters.
The charged particle optical apparatus may be configured so that the relative potential between the third electrode and the fourth electrode is adjustable, in particular controllably adjustable. The charged particle optical apparatus may further be configured so that in the inspection operation mode, the third electrode is at a positive potential relative to the fourth electrode. The charged particle optical apparatus may further be configured so that in the inspection operation mode, the third electrode is at a potential relative to the fourth electrode of at least +30 V, or at least +50 V, or at least +100 V. In the inspection operation mode, the third electrode may be at a potential relative to the fourth electrode of less than +3000 V, or less than +1000 V, or less than +800 V, or less than +600 V.
Thereby, a sufficient portion of secondary electrons which have passed through the differential pressure aperture of the fourth electrode is guided through the differential pressure aperture of the third electrode.
Additionally or alternatively, the charged particle optical apparatus may be configured so that the fourth electrode can be maintained at a positive potential level of more than 20 V or more than 50 V or more than 100 V relative to an abutment portion of an object holder to which the object is abuttingly attached.
Since the object is abuttingly attached to the abutment portion of the object holder, at least a portion of the object is maintained at the potential of the abutment portion. The relative potential between the fourth electrode and the abutment portion may be adjustable, in particular controllably adjustable. The fourth electrode and/or the abutment portion of the object holder may be electrically connected to a voltage source which is configured for adjustment of the relative potential between the fourth electrode and the abutment portion of the object holder.
This allows adjustment of the potential levels so that a sufficient portion of secondary electrons, which are emitted from the object, are guided through the differential pressure aperture of the fourth electrode. Furthermore, this allows adjustment of the potential levels so that a gas cascade is generated between the object and the fourth electrode. This gas cascade can provide the gas amplification for a gaseous detector, which is mounted within the pressure-controlled interior of the specimen chamber. Additionally or alternatively, this gas cascade generates secondary electrons which are guided through the differential pressure apertures of the third and fourth electrode so that they can be detected by the particle detector.
The third and fourth electrodes may be part of a differential pressure module, which is positionable within the pressure-controlled interior of the specimen chamber. The differential pressure module may include an intermediate vacuum hone which is disposed between the differential pressure aperture of the third electrode and the differential pressure aperture of the fourth electrode. The fourth electrode may be exchangeably attached to the differential pressure module. Thereby, it is possible to provide a plurality of final electrodes, wherein each of the final electrodes can be selectively attached to the differential pressure module so as to serve as the fourth electrode.
By way of example, one of the final electrodes has a differential pressure aperture which is adapted for imaging objects at vacuum pressure levels in the pressure-controlled interior of the specimen chamber of 600 Pa or more. This final electrode can therefore be used to inspect wet objects. Additionally or alternatively, one of the final electrodes has a differential pressure aperture which is adapted for imaging at vacuum pressure levels in the specimen chamber of between 30 Pa and 150 Pa. This final electrode can therefore be used to inspect objects which tend to accumulate charges. Both of these final electrodes are configured for imaging using the particle detector which detects particles which have passed through the differential pressure apertures of the third and the fourth electrode.
Additionally or alternatively one of the final electrodes has a comparatively large differential pressure aperture diameter and is configured for inspecting samples which tend to accumulate charges, wherein the objective lens operates without an electric objective lens field and detection of particles, which have passed through the differential pressure apertures of the first and the second electrode, is deactivated. Accordingly, this final electrode may be used for imaging using a gaseous detector which is disposed in the pressure-controlled interior of the specimen chamber.
According to an embodiment, an inner peripheral edge of the differential pressure aperture of the fourth electrode has a thickness of less than 300 micrometers or less than 50 micrometers. The thickness may be greater than 0.4 micrometers. The edge may be cylindrical, substantially cylindrical or may be a sharp edge. The sharp edge may be formed by a tapered surface.
At least a portion of the fourth electrode may form at least a portion of a detector. By way of example, at least a portion of the fourth electrode may form a collector electrode. The collector electrode may be part of a gaseous particle detector and/or may be configured to collect electrons without gaseous amplification. Additionally or alternatively, at least a portion of the fourth electrode may consist of semiconductor material and may form part of a semiconductor particle detector.
According to a further embodiment, the fourth electrode is operable at a different potential level than the first, second and third electrodes.
According to a further embodiment, the third and fourth electrodes are configured so that a potential difference applied between the third electrode and the fourth electrode causes a focusing and/or collecting electric field for the emitted particles.
According to a further embodiment, at least a portion of the second electrode is a magnetic pole piece portion of the objective lens and/or s formed at least partially from magnetic material. According to a further embodiment, the second electrode is electrically connected to the potential of a magnetic pole piece of the objective lens. Additionally or alternatively, the second electrode may be maintained at a same or substantially same potential as the magnetic pole piece. The magnetic pole piece may be an outer and/or object-side magnetic pole piece of the objective lens.
According to a further embodiment, in an inspection operation mode of the charged particle optical apparatus, the objective lens field has a magnetic field strength which is greater than 10 mT, or greater than 15 mT, or greater than 20 mT, measured at a location where the primary particle beam path enters into the vacuum zone of the pressure-controlled interior of the specimen chamber. The location may be a position of a final differential pressure aperture, such as the differential pressure aperture of the fourth electrode.
According to a further embodiment, the third and/or fourth electrodes are part of a differential pressure module. The charged particle apparatus may further comprise a positioning mechanism, which is at least partially arranged in the pressure-controlled interior of the specimen chamber. The positioning mechanism may be configured to selectively position the differential pressure module within the pressure-controlled interior of the specimen chamber into an operating position in which the primary particle beam path passes through the differential pressure aperture of the third electrode and/or the differential pressure aperture of the fourth electrode. The selective positioning may include an advancing movement of the differential pressure module directed toward the primary particle beam path.
According to a further embodiment, the positioning mechanism includes a positioning arm. The advancing movement may be transmitted to the differential pressure module by a track-guided movement of the positioning mechanism and/or positioning arm.
According to an embodiment, during the positioning of the differential pressure module, the second electrode remains fixed in relation to the primary particle beam path.
According to a further embodiment, the positioning of the differential pressure module comprises bringing the differential pressure module into abutment with an abutment portion of the charged particle optical apparatus. The second electrode may include at least a portion of the abutment portion.
According to a further embodiment, the differential pressure module may include a third electrode and a fourth electrode, each having a differential pressure aperture through which the primary particle beam path passes. The third and fourth differential pressure apertures may be operable at different potential levels relative to each other.
The particle detector for detecting emitted particles which pass through the differential pressure aperture of the third electrode and/or the differential pressure aperture of the fourth electrode may be a non-gaseous particle detector. In other words, the particle detector may be configured to operate without using gaseous amplification, also denoted as gas cascade amplification. Thereby, the particle detector can be operated in vacuum zones of low vacuum pressure, such as in the first vacuum zone or in a vacuum zone, which is located upstream of the first vacuum zone relative to the primary particle beam path.
According to a further embodiment, the particle detector for detecting emitted particles which pass through the third electrode includes a solid impact recording medium. The solid impact recording medium may be an amplifying solid impact recording medium. The solid impact recording medium may be configured for performing secondary emission amplification, scintillation amplification, and/or charge carrier amplification.
The solid impact recording medium which performs secondary emission amplification may be part of a secondary electron multiplier. By way of example, the solid impact recording medium may be a dynode (such as the dynode of a channeltron detector), a micro channel plate, a microsphere plate. The solid impact recording medium which performs scintillation amplification may be scintillator, such as a plastic scintillator, a YAG sinctillator and/or a YAP scintillator. The solid impact recording medium which performs charge carrier amplification may be an active semiconductor region of a semiconductor particle detector. The charge carriers may be electrons and/or electron-hole pairs. The semiconductor detector may for example have a metal-semiconductor junction and/or a p-n junction.
Additionally or alternatively, the particle detector for detecting emitted particles which pass through the third electrode may include one or a combination of the following: a photomultiplier, a photodiode, an avalanche photodetector (APD), a CCD photodetector and a CMOS photodetector.
According to an embodiment, the charged particle optical apparatus may include one or more chamber-mounted detectors, which are disposed in the pressure-controlled interior of the vacuum chamber and which are configured to detect particles and/or radiation. Examples for such radiation and/or particle detectors are EDX (energy dispersive X-ray) detectors, WDS (wavelength dispersive spectroscopy) detectors, gaseous detectors and cathodoluminescence detectors. The gaseous detector may be configured as a collector electrode detector and/or a gas scintillation detector.
The charged particle optical apparatus may include a cooling system for cooling the object. The cooling system may be configured to maintain the object at a temperature of less than 10 degrees Celsius or less than 5 degrees Celsius or less than 1 degree Celsius. By cooling wet objects to a temperature within these temperature ranges allows maintaining a low vacuum pressure level in the pressure-controlled interior of the specimen chamber.
Embodiments provide a method of operating the charged particle optical apparatus. The method may include adjusting potential levels of the first, second and/or third electrodes so that the potential levels are different from each other. Additionally or alternatively, the method may include detecting emitted particles, which are emitted from the object and which pass through the differential pressure aperture of the third electrode.
Embodiments provide a method of operating a charged particle optical apparatus. The charged particle optical apparatus may include a differential pressure module having at least a first differential pressure aperture. The method may include acquiring a first image with the differential pressure module positioned in a non-operating position in which the first differential pressure aperture is outside the primary particle beam path. The method may include positioning the first differential pressure aperture within the pressure-controlled interior of the specimen chamber from the non-operating position into an operating position. When the first differential pressure aperture is in the operating position, the primary particle beam path may enter into the pressure-controlled interior of the specimen chamber by passing through the first differential pressure aperture. The method may further include acquiring a second image with the differential pressure module positioned in the operating position. At least a portion of the first image and at least a portion of the second image may represent a same object portion of the object.
The positioning of the first differential pressure aperture within the pressure-controlled interior allows in an efficient manner acquisition of images of an object portion with and without the differential pressure aperture being positioned in the operating position. It turned out that such images provide complementary information for image interpretation. Hence, more thorough and efficient inspection procedures can be performed.
The differential pressure module may include a second differential pressure aperture. In the operating position of the differential pressure module, the second differential pressure aperture may be disposed between the first differential pressure aperture and the object. In the non-operating position of the differential pressure module, the second differential pressure aperture is outside the primary particle beam path. Between the first and the second differential pressure apertures, an intermediate vacuum zone may be disposed.
According to an embodiment, the first image is acquired using a gaseous detector. Additionally or alternatively, the second image is acquired using a detector, which is configured to detect emitted particles, which pass through the first and/or second differential pressure aperture. The detector, which is used for acquiring the second image may be a through-the-lens detector, in particular a through-the-lens secondary electron detector.
According to an embodiment, a pressure level in the pressure-controlled interior of the specimen chamber, measured when the second image is acquired, is more than 1.5 times, or more than 2 times, or more than 5 times, or more than 10 times the pressure level measured when the first image is acquired. Additionally or alternatively, the pressure level in the pressure-controlled interior of the specimen chamber when the first image is acquired is less than 80 Pa, or less than 60 Pa, or less than 30 Pa. Additionally or alternatively, the vacuum pressure level in the pressure-controlled interior of the specimen chamber when the first and the second images are acquired may be greater than 5 Pa, or greater than 15 Pa, or greater than 25 Pa.
According to a further embodiment, the method further includes combining at least a portion of the first image and at least a portion of the second image. The combination may be a weighted combination. Generating the combination may include generating a combined image. Generating the combination may include forming a pixel-by-pixel sum, a weighted pixel-by-pixel sum, a pixel-by-pixel difference and/or a weighted pixel-by-pixel difference. The weight assigned to the first and/or the second image may vary across the respective image. The weight assigned to an image may vary across the image. The graphical user interface may be configured so that the user can adjust parameters for the combination of the images. By way of example, one or more weight factors for the weighted combination may be adjustable through the graphical user interface. The weighted combination may be formed by assigning an individual weight for each of a plurality of pixels of the first and/or the second image.
Additionally or alternatively, the method may include combining an image portion of the first image and an image portion of the second image, wherein the portions represent complementary or substantially complementary, non-overlapping or substantially non-overlapping object portions.
According to a further embodiment, the combining of at least the portion of the first image and at least the portion of the second image comprises identifying an image region of the second image which includes all those portions of the second image in which the primary particle beam path is influenced by a physical and/or electrostatic interaction with the differential pressure aperture.
The physical and/or electrostatic interaction with the differential pressure aperture may cause a shadowing or attenuation of the primary particle beam and/or may cause aberrations of the primary particle beam induced by the electric field generated by the presence of the differential pressure aperture.
According to a further embodiment, the combining of at least the portion of the first image and at least the portion of the second image is performed to form a combined image. In the combined image, a contribution of the identified image region of the second image may be suppressed relative to the contribution of at least a portion of the remaining image. In particular, the identified image region may be assigned a low weight compared to at least a portion of the remaining image. The contribution of the identified image region may be suppressed in a manner so that the contribution is absent. The contribution of a pixel of an image (such as a pixel of the first or the second image) to a corresponding pixel of the combined image may be defined as a weight factor which is assigned to the pixel data value of the pixel of the image. The corresponding pixel of the combined image may represent a same object location as the pixel of the image.
According to a further embodiment, the combining of at least the portion of the first image and at least the portion of the second image is performed to form a combined image. A contribution of pixels of the second image to the combined image is suppressed, at least for those pixels in the second image where in the second image the primary particle beam path is influenced by physical and/or electrostatic interaction with the differential pressure aperture. The contribution of these pixels may be suppressed relative to a contribution of at least a portion of the remaining pixels of the second image. The remaining pixels are remaining relative to the suppressed image portion.
According to a further embodiment, the method further comprises identifying the portion of the first image and the portion of the second image which represent the same object portion. The identifying of the portion of the first image and the portion of the second image may include determining a parameter of a position and/or an orientation of a field of view represented by the second image measured relative to a position and/or orientation of a field of view represented by the first image.
According to an embodiment, during the acquiring of the first and/or the second image, the objective lens field has a magnetic field strength which is greater than 10 mT, or greater than 15 mT, or greater than 20 mT, measured at a location where the primary particle beam path enters into the vacuum zone of the pressure-controlled interior of the specimen chamber.
Embodiments provide a method of operating a charged particle optical apparatus. The charged particle optical apparatus may include a differential pressure aperture disposed in the beam path of the primary particle beam. The primary particle beam path may enter into the pressure-controlled interior of the specimen chamber by passing through the differential pressure aperture. The method may include acquiring a third image using a detector which is disposed in the specimen chamber. The method may include acquiring a fourth image using a detector which is configured to detect emitted particles which are emitted from the object and which pass through the differential pressure aperture. At least a portion of the third image and at least a portion of the fourth image may represent a same object portion of the object.
This allows for more efficient and thorough inspection procedures, since the image data acquired by the different detectors provide complementary information for image interpretation.
The use of the terms first, second, etc. in this disclosure do not denote any order or importance. Rather these terms are used to distinguish elements from each other. Therefore, the expression “third image” does not necessarily mean that a first and a second image have been acquired.
According to a further embodiment, the method further includes generating a combination of at least a portion of the third image and at least a portion of the fourth image. The combination may be a weighted combination. The combining may include forming a pixel-by-pixel sum or weighted sum and/or a pixel-by-pixel difference or weighted difference. The weight assigned to an image may vary across the image. The graphical user interface may be configured so that the user can adjust parameters for the combination of the images. By way of example, one or more weight factors for the weighted combination may be adjustable through the graphical user interface. The weighted combination may be formed by assigning an individual weight for each of a plurality of pixels of the third and/or the fourth image.
According to an embodiment, the detector, which is disposed in the specimen chamber, is a gaseous detector. The gaseous detector may be a side-mounted detector. Additionally or alternatively, the detector, which is configured to detect emitted particles which are emitted from the object and which pass through the differential pressure aperture, may be a through-the-lens detector. The detector, which is configured to detect emitted particles, which pass through the differential pressure aperture may also detect electrons generated by gas cascade amplification.
The charged particle optical apparatus may include a second differential pressure aperture. The second differential pressure aperture may be disposed in the primary particle beam path. The detector, which is used for acquiring the fourth image may be configured to detect emitted particles, which pass through the differential pressure aperture and through the second differential pressure aperture.
According to a further embodiment, the combining is performed to generate a combined image. At least a portion of the combined image may show one or more intensity valleys, which correspond or substantially correspond to one or more intensity valleys of the third image. In the portion of the combined image, a contribution of the fourth image may be enhanced within the one or more intensity valleys compared to outside the one or more intensity valleys. In this context, the term “corresponding” may be defined to mean that the intensity valleys represent a same or substantially a same object portion.
The terms shadow region and/or intensity valleys may be defined to mean an image region, which is at least partially surrounded by an intensity edge. The shadow region and/or intensity valley may represent an intensity variation above noise level. The shadow region and/or intensity valley may include in image region having an intensity of less than 80%, less than 70%, less than 60%, or less than 50%, compared to the intensity of the intensity edge. The image region may include a plurality of pixels. The plurality of pixels may form a pixel cluster.
The intensity shadow region may be an intensity valley. The third and/or the fourth images may be grayscale images and/or color images. The intensity may be a grayscale value or may be determined depending on the grayscale value of the third image. Additionally or alternatively, the intensity may be a value of a channel of a pixel, which carries brightness information of a pixel, or may be determined depending on the value of the channel, which carries the brightness information. By way of example, the intensity may be a value of a luminance channel or may be determined depending on the value of the luminance channel.
According to a further embodiment, at least a portion of the combined image may show one or more colored regions, which correspond or substantially correspond to one or more intensity valleys of the third image. In the portion of the combined image, a contribution of the fourth image may be enhanced within the one or more colored regions compared to outside the one or more colored regions. In this context, the term “corresponding” may be defined to mean that the colored regions of the combined image and the shadow regions of the third image represent a same or substantially a same object portion. In the portion of the combined image, compared to outside of the colored regions, the colored regions may be marked with different values of parameters of color appearance, such as colorfulness, chroma, saturation, lightness, and brightness.
According to a further embodiment, at least a portion of the combined image may show one or more shadow regions, which correspond to one or more shadow regions of the third image. In the portion of the combined image, a contribution of the fourth image may be enhanced within the one or more shadow regions compared to outside the one or more shadow regions. In this context, the term “corresponding” may be defined to mean that the shadow regions represent a same or substantially a same object portion.
Additionally or alternatively, the method may further comprise determining at least one contribution image region within the fourth image. The contribution image region may contribute to the combined image. The contribution image region may be determined depending on image data values of the third image. The determining of the contribution image region depending on the image data values of the third image may be performed so that an image region of the third image, which corresponds to the contribution image region of the fourth image, represents at least a portion of a shadow region and/or an intensity valley of the third image. In this context, the term “corresponding” may be defined to mean that both image regions represent a same or substantially a same object portion.
An image region in the combined image, which corresponds to the contribution image region of the fourth image may represent at least a portion of a shadow region and/or an intensity valley of the combined image. The data analysis system may include a graphical user interface. The graphical user interface may be configured to receive user input and to adjust, depending on the user input, one or more parameters of the contribution of the third image relative the contribution of the fourth image within the shadow region and/or intensity valley of the combined image.
According to an embodiment, during the acquiring of the third and/or fourth image, the objective lens field has a magnetic field strength which is greater than 10 mT, or greater than 15 mT, or greater than 20 mT, measured at a location where the primary particle beam path enters into the vacuum zone of the pressure-controlled interior of the specimen chamber.
Embodiments provide a charged particle optical apparatus. The charged particle optical apparatus includes a particle optical arrangement configured to define a primary particle beam path for inspecting an object. The charged particle optical apparatus further includes a specimen chamber configured to accommodate an object in a pressure-controlled interior of the specimen chamber during the inspection of the object. The charged particle optical apparatus may further include a differential pressure module having a differential pressure aperture. The charged particle optical apparatus may include a positioning arm being at least partially arranged in the specimen chamber and configured to selectively position the differential pressure module within the pressure-controlled interior of the specimen chamber into an operating position. In the operating position, the primary particle beam path may pass through the differential pressure aperture. The selective positioning may include an advancing movement of the differential pressure module directed in a direction toward a section of the primary particle beam path, which is within the specimen chamber. The advancing movement may be transmitted to the differential pressure module by a track-guided movement of the positioning arm.
Accordingly, a charged particle optical apparatus is provided, which allows selectively disposing a differential pressure aperture in the primary particle beam path in an efficient manner. This enables fast switching between two operation modes, which may be provided for inspecting objects at different pressure level ranges in the specimen chamber. By way of example, the first operation mode is configured for pressure levels of 0.01 Pa or lower in the specimen chamber and the second operation mode is configured for pressure levels higher than 0.01 Pa in the specimen chamber. It is a further advantage that the track-guided movement of the positioning arm leaves plenty of space in the interior of the specimen chamber for further components of the particle optical apparatus, such as detectors and gas supply systems.
The charged particle optical apparatus may be a particle microscope, in particular a scanning particle microscope. The scanning particle microscope may be a scanning electron microscope and/or a focused ion beam microscope. The focused ion beam microscope may comprise a gas field ion source, a plasma ion source and/or a liquid metal ion source. By way of example, the focused ion beam microscope is a noble gas ion microscope, in particular a helium ion microscope.
The particle optical arrangement may be configured to focus the primary particle beam on a surface of the object. The particle optical arrangement may be configured to scan the primary particle beam across the surface of the object. The particle optical arrangement may include an objective lens, a condenser lens, a beam booster, a particle gun and/or a deflector system. The deflector system may be configured to deflect the primary particle beam. The objective lens may be configured as an electrostatic lens, as a magnetic lens or as a combined magnetic-electrostatic objective lens.
The specimen chamber may be configured as a vacuum chamber. The specimen chamber may be configured to hermetically separate the interior of the specimen chamber from the surrounding atmosphere. The specimen chamber may include a vacuum port for evacuating the specimen chamber. The vacuum port may be in fluid communication with a vacuum source. The interior of the specimen chamber may be configured as a single vacuum zone. The charged particle optical apparatus may include a plurality of vacuum zones. The vacuum zones may be generated by differential pumping. Each of the vacuum zones may have a substantially uniform vacuum pressure level. Each of the vacuum zones may be undivided by differential pressure apertures.
The differential pressure aperture of the differential pressure module may have a width, which is in a range of between 50 micrometers and 2000 micrometers or which is in a range of between 100 micrometers and 1000 micrometers. The width may be measured in a direction perpendicular to the primary particle beam path. The differential pressure aperture may have a length, which is in a range of between 20 micrometers and 10 millimeters, or in a range of between 50 micrometers and 10 millimeters, or in a range of between 100 micrometers and 10 millimeters. The length may be measured in a direction parallel to the primary particle beam path. The differential pressure aperture may be formed in a foil and/or plate.
The differential pressure module may be configured such that in the operating position, the differential pressure aperture separates two vacuum zones of the charged particle optical apparatus. Through the differential pressure aperture, the primary particle beam path may enter into the interior of the specimen chamber. With the differential pressure module being disposed in the operating position, a differential pressure drop may be maintainable across the differential pressure aperture. A pressure ratio P2/P1 across the differential pressure aperture may be below 0.5, below 0.1, or below 0.01, or below 0.001. P1 may be defined as the pressure level of the vacuum zone of the interior of the specimen chamber. P2 may be defined as the pressure level of the vacuum zone, which is separated from the interior of the specimen chamber by the differential pressure aperture.
The charged particle optical apparatus may be switchable to a first and a second operation mode. In the first operation mode, the differential pressure module may be disposed in a non-operating position. In the second operation mode, the differential pressure module may be disposed in the operating position. The charged particle optical apparatus may include a controller, which is configured to switch the particle optical apparatus to the first and/or to the second operation mode.
Prior systems have coupled objects to an electron beam source in a specimen chamber, for example the system as described in U.S. Pat. No. 8,148,684 (Yoshikawa). In Yoshikawa an aperture member is detachably coupled to an electron beam source by a certain mechanism for moving the object. However, the instant invention offers a novel and unique system for moving the differential pressure module to different positions in relation to the first and second operation mode. The presented novel and unique system for moving the differential pressure module allows for rapid positioning of the differential pressure module into the different positions with higher accuracy than prior systems.
The positioning of the differential pressure module within the specimen chamber is performed in the vacuum-controlled environment. In other words, the positioning may be performed while the interior of the specimen chamber is evacuated, i.e. the specimen chamber may not need to be vented during the positioning process.
The positioning arm may have a longitudinal shape. During at least a portion of the positioning, a first portion of the positioning arm may be disposed in a surrounding atmosphere of the charged particle optical apparatus and/or a second portion of the positioning arm may be disposed in the specimen chamber. During at least a portion of the positioning, the positioning arm may extend through a vacuum enclosure of the particle optical apparatus. In other words, the positioning arm may extend from outside the vacuum enclosure to inside the vacuum enclosure. The vacuum enclosure may separate the vacuum from the surrounding atmosphere. The track-guided movement of the positioning arm may include inserting at least a portion of the positioning arm into the specimen chamber.
The positioning arm may be a rigid body. The positioning arm may be an elongate body extending along a longitudinal axis of the positioning arm. A portion or all of the positioning arm may substantially be in the form of a bar. By way of example, the bar is a square and/or a round bar. The track-guided movement may advance and/or approach the positioning arm toward a segment of the primary beam path, which extends inside the specimen chamber. In other words, the track-guided movement may be directed toward the segment of the primary beam path. The longitudinal axis of the positioning arm may be oriented transverse, substantially perpendicular or perpendicular to a direction of the primary beam path, wherein the direction of the primary beam path is measured at a location within the specimen chamber. Additionally or alternatively, the longitudinal axis of the positioning arm may be oriented at an angle relative to a plane, which is perpendicular to the direction of the primary beam path, wherein the angle is smaller than 80 degrees, or smaller than 70 degrees, or smaller than 60 degrees, or smaller than 50 degrees, or smaller than 40 degrees, or smaller than 30 degrees, or smaller than 20 degrees, or smaller than 10 degrees, or smaller than 5 degrees.
The track-guided movement may be a longitudinal movement or a substantially longitudinal movement of the positioning arm. A direction of the track-guided movement may be oriented parallel or substantially parallel to the longitudinal axis of the positioning arm. An angle between the longitudinal axis of the positioning arm and the direction of the track-guided movement of the positioning arm may be less than 80 degrees, or less than 70 degrees, or less than 60 degrees, or less than 50 degrees, or less than 40 degrees, or less than 30 degrees, or less than 20 degrees, or less than 10 degrees, or less than 5 degrees, or less than 2 degrees. The angle may vary with the positioning of the differential pressure module. The track-guided movement, may be configured so that an orientation of the positioning arm relative to the longitudinal axis of the positioning arm is kept constant or substantially constant. In other words, the track-guided movement may be configured so that the positioning arm does not or substantially does not rotate about its longitudinal axis.
The charged particle optical apparatus may include a guide configured to guide the advancing movement of the differential pressure module and/or the track-guided movement of the positioning arm. The guide may define a guiding path. The guiding path may extend along a guide track of the guide. The guide track may be formed by a rail of the guide. Thereby, the guiding path may extend along a rail of the guide.
At least a portion of the guide, at least a portion of the rail, at least a portion of the guide track and/or at least a portion of the guiding path may be disposed outside of the specimen chamber and/or in a surrounding atmosphere of the charged particle optical apparatus. Additionally or alternatively, at least a portion of the guide, at least a portion of the rail, at least a portion of the guide track and/or at least a portion of the guiding path may be disposed inside the specimen chamber. At least a portion of the rail, at least a portion of the guide track and/or at least a portion of the guiding path may be oriented transverse, substantially perpendicular to, or perpendicular to a direction of the primary beam path, wherein the direction is measured at a location within the specimen chamber. The guide track may be formed by the rail and/or by the positioning arm. Additionally or alternatively, at least a portion of the rail may be oriented at an angle relative to a plane, which is perpendicular to the direction of the primary beam path, wherein the angle is smaller than 80 degrees, or smaller than 70 degrees, or smaller than 60 degrees, or smaller than 50 degrees, or smaller than 40 degrees, or smaller than 30 degrees, or smaller than 20 degrees, or smaller than 10 degrees, or smaller than 5 degrees. Additionally or alternatively, at least a portion of the guide track may be oriented at an angle relative to a plane, which is perpendicular to the direction of the primary beam path, wherein the angle, is smaller than 80 degrees, or smaller than 70 degrees, or smaller than 60 degrees, or smaller than 50 degrees, or smaller than 40 degrees, or smaller than 30 degrees, or smaller than 20 degrees, or smaller than 10 degrees, or smaller than 5 degrees. Additionally or alternatively, at least a portion of the guiding path may be oriented at an angle relative to a plane, which is perpendicular to the direction of the primary beam path, wherein the angle, is smaller than 80 degrees, or smaller than 70 degrees, or smaller than 60 degrees, or smaller than 50 degrees, or smaller than 40 degrees, or smaller than 30 degrees, or smaller than 20 degrees, or smaller than 10 degrees, or smaller than 5 degrees.
The direction of the primary beam path may be measured at a location within the specimen chamber.
The guiding path may have two ends. In other words, the guide may be configured so that the guiding path does not form a loop. The guiding path may be longitudinal, substantially linear, linear and/or curved.
The guide may include two mating guide members. The first guide member may be configured as a rail, may form a guide track and/or may define a guiding path. The second guide member may be configured as a carriage and/or may be configured to be movable along the guiding path and/or the guide track. The carriage may be a slide carriage and/or a roller carriage. The positioning arm may be configured as a guide member, such as a rail of the guide. Thereby, the positioning arm may form a guide track. The guiding path may be defined as a path along which one of the mating guide member travels.
The positioning arm may be rigidly connected to a guide member of the two mating guide members. The guide member to which the positioning arm is rigidly connected may travel along a rail and/or a guiding path of the guide, may be a carriage and/or may be a rail.
The differential pressure module may be abuttingly, rigidly and/or movably attached to the positioning arm. The positioning arm may be configured to position the differential pressure module between the non-operating position and the operating position. In the non-operating position, the differential pressure module may be disposed spaced apart from a segment of the primary particle beam path, which extends inside the specimen chamber.
The advancing movement may approach the differential pressure module toward a segment of the primary particle beam path, which extends inside the specimen chamber. In other words, the advancing movement may be directed toward the segment of the primary beam path. During the positioning and/or during the advancing movement, the differential pressure module may be brought into abutment with an abutment portion. In the operating position, the differential pressure module may be abutted against the abutment portion. The abutment portion may be a portion of the objective lens and/or may be rigidly connected to the objective lens, such as a housing, which at least partially accommodates the objective lens. Additionally or alternatively, during the advancing movement, the differential pressure module may be brought into intersection with the primary particle beam path within the specimen chamber. A final position of the advancement movement may be the operating position of the differential pressure module. Additionally or alternatively, in the final position of the advancing movement, the differential pressure module may touch the abutment portion. The advancing movement may bring the differential pressure module into sealing engagement with the abutment portion.
According to an embodiment, a direction of the advancing movement of the differential pressure module and/or a direction of the track-guided movement of the positioning arm is oriented transverse to, substantially perpendicular to, or perpendicular to a direction of the particle beam path measured at a location within the specimen chamber. Additionally or alternatively, the direction of the advancing movement of the differential pressure module may be oriented at an angle relative to a plane, which is perpendicular to the direction of the primary beam path, wherein the angle is smaller than 80 degrees, or smaller than 70 degrees, or smaller than 60 degrees, or smaller than 50 degrees, or smaller than 40 degrees, or smaller than 30 degrees, or smaller than 20 degrees, or smaller than 10 degrees, or smaller than 5 degrees. Additionally or alternatively, the direction of the track-guided movement of the positioning arm may be oriented at an angle relative to a plane, which is perpendicular to the direction of the primary beam path, wherein the angle is smaller than 80 degrees, or smaller than 70 degrees, or smaller than 60 degrees, or smaller than 50 degrees, or smaller than 40 degrees, or smaller than 30 degrees, or smaller than 20 degrees, or smaller than 10 degrees, or smaller than 5 degrees.
According to an embodiment, the advancing movement of the differential pressure module and/or the track-guided movement of the positioning arm is a substantially translational, a translational, or a combined translational and rotational movement.
According to an embodiment, the positioning of the differential pressure module includes performing, after completion of the advancing movement, a pressing movement of the differential pressure module for pressing the differential pressure module against the abutment portion. The pressing movement may be directed toward the abutment portion. A pressing force for pressing the differential pressure module against the abutment portion may be transmitted by the positioning arm. The pressing movement may compress a resilient sealing element of the differential pressure module. The pressing movement may bring the differential pressure module into sealing engagement with the abutment portion.
The pressing movement of the differential pressure module may be performed substantially in a direction parallel to a direction of the primary particle beam path measured at a location within the specimen chamber. The pressing movement may be transmitted to the differential pressure module by a rotational movement, a pivoting movement, a substantially translational movement and/or a translational movement of the positioning arm. The final position of the pressing movement may be the operating position. The starting position of the pressing movement may be the final position of the advancing movement. In the starting position of the pressing movement, the differential pressure module may touch the abutment portion.
According to an embodiment, the differential pressure module comprises a module-mounted detector for detecting particles and/or radiation.
The module-mounted detector may be rigidly and/or abuttingly attached to the remaining portion of the differential pressure module. The module-mounted detector may be advanced toward the primary particle beam path by the advancing movement. In the operating position of the differential pressure module, one or more particle and/or radiation receiving surfaces of the module-mounted particle detector may be disposed in the interior of the specimen chamber. In the operating position of the differential pressure module, one or more of the particle and/or radiation receiving surfaces of the module-mounted particle detector may be arranged circumferentially around the primary particle beam path.
The module-mounted detector may be configured to detect emitted particles, which are emitted from the object. The emitted particles may be primary particles and/or object particles. The module-mounted detector may be configured to selectively detect primary particles and/or object particles. Primary particles may be defined as particles of the primary particle beam, which are backscattered by the object, such as backscattered electrons. Object particles may be defined as particles of the object, which are released from the object when impacted by the primary particle beam. By way of example, the object particles are secondary ions and/or secondary electrons. The module-mounted detector may include one or a combination of a semiconductor detector, a scintillator detector, a gaseous detector, a four quadrant (4Q) detector and a metal electrode detector for measuring the particle current impinging on the metal electrode. Additionally or alternatively, the module-mounted detector may be configured to detect radiation, such as cathodoluminescence radiation emitted from the interaction region.
According to an embodiment, at least a portion of the differential pressure aperture is formed by a component of the module-mounted detector, which contributes to a generation of a detector signal in response to receiving particles and/or radiation. The particles and/or radiation may be received on a particle and/or radiation receiving surface of the module-mounted detector. By way of example, the component is a portion of a semiconductor substrate of a semiconductor particle detector or a portion of a scintillator of a scintillator detector.
According to a further embodiment, during the positioning of the differential pressure module and/or during the advancing movement of the differential pressure module, at least a portion of the positioning arm passes through at least a portion of an opening extending through a wall portion of the specimen chamber. Additionally or alternatively, during the positioning of the differential pressure module and/or during the advancing movement, a portion of a driving member of the particle optical apparatus, which is drivingly coupled to the positioning arm, may pass through at least the portion of the opening.
The driving member may be rigidly and/or movably connected to the positioning arm. The advancing movement of the differential pressure module may be transmitted by a movement of the driving member. The movement of the driving member may be track-guided. During at least a portion of the positioning of the differential pressure module, the positioning arm and/or the driving member may extend through the vacuum enclosure. A surface normal of the wall portion may be oriented parallel or substantially parallel to a longitudinal axis of the driving member and/or a longitudinal axis of the positioning arm.
According to an embodiment, a degree of freedom of the positioning arm for performing at least a portion of the positioning of the differential pressure module or at least a portion of the pressing movement is provided by a guide clearance of the guide for guiding the track-guided movement of the positioning arm. The guide clearance may be a clearance between mating guide members of the guide and/or may be a transversal clearance relative to a track of the guide. In other words, a degree of freedom provided by the clearance may be oriented perpendicular to a direction of the track of the guide.
According to a further embodiment, in the operating position, a conductive portion of the differential pressure module is electrically isolated from the abutment portion. The charged particle optical apparatus may include a voltage source, which is configured to place the conductive portion at a pre-defined potential. The pre-defined potential may be different from a potential of the abutment portion.
According to a further embodiment, the charged-particle optical apparatus is configured to pivot the positioning arm about a pivoting axis. The pivoting axis may be arranged outside and/or inside of the specimen chamber.
According to an embodiment, the differential pressure module comprises a seal member for bringing the differential pressure module into sealing engagement during the positioning of the differential pressure module.
The seal member may comprise a deformable and/or resilient sealing element. Additionally or alternatively, the seal member may comprise a seating surface. The seating surface may mate with a mating seating surface provided at the abutment portion. The seating surface and/or the mating seating surface may be rigid. During the positioning of the differential pressure module, the seating member may be brought into attachment with a sealing member, which may be provided at the abutment portion. The positioning of the differential pressure module, the advancing movement and/or the pressing movement of the differential pressure module may bring the differential pressure module into sealing engagement with the abutment portion. The sealing element may be in the form of a single loop, such as a ring. In the operating position, the loop may surround the primary particle beam path. By way of example, the resilient sealing element is an O-ring. The O-ring may be made of Viton.
According to an embodiment, the differential pressure module comprises an intermediate vacuum zone, wherein in the operating position, the primary particle beam path passes through the intermediate vacuum zone.
The intermediate vacuum zone may comprise a vacuum port for evacuating the intermediate vacuum zone. At least when the differential pressure module is in the operating position, the vacuum port may be in fluid communication with a vacuum source. The vacuum source may be a vacuum pump. The vacuum port may be connected to the vacuum source via a vacuum line. The vacuum port may be arranged outside of the primary particle beam path. In other words, the primary particle beam path does not pass through the vacuum port. The vacuum line may be formed by the positioning arm and/or may be rigidly and/or movably attached to the positioning arm. The vacuum line may extend through an interior of the specimen chamber. The vacuum line may extend along at least a portion of the positioning arm. The vacuum line may be moved in conjunction with the track-guided movement of the positioning arm.
It is also conceivable that the vacuum line is rigidly connected to the particle optical arrangement. In such an embodiment, the vacuum zone of the differential pressure module may be brought into fluid communication with the vacuum line by the positioning of the differential pressure module into the operating position.
Through the differential pressure aperture, the primary particle beam path may exit from the intermediate vacuum zone and enter into the interior of the specimen chamber. The differential pressure module may comprise a further differential pressure aperture through which the primary particle beam path may enter into the intermediate vacuum zone.
According to a further embodiment, the differential pressure module comprises two intermediate vacuum zones. In the activation position of the differential pressure module, the primary particle beam path may pass sequentially through the two intermediate vacuum zones.
The two intermediate vacuum zones may be separated from each other by a separating differential pressure aperture. When the differential pressure module is in the operating position, the primary particle beam path may pass through the separating differential pressure aperture.
According to an embodiment, each of the two intermediate vacuum zones comprises a vacuum port for evacuating the respective vacuum zone. Each of the vacuum ports may be in fluid communication with a separate or common vacuum source. The charged particle optical apparatus may comprise a branched vacuum line having two branch lines. For each of the branch lines, an end of the respective branch line may open into a separate one of the two vacuum ports.
According to a further embodiment, in the operating position, the differential pressure aperture is located between a final magnetic lens of the particle optical arrangement and an object plane of the particle optical arrangement and/or between a principal plane of the final magnetic lens and the object plane. The term “between a final magnetic lens and the object plane” may be defined as being located between all pole pieces of the final magnetic lens on the one hand and the object plane on the other hand. The object plane may be located inside the specimen chamber. The particle optical arrangement may be configured to focus the primary particle beam on the object plane. The final magnetic lens may be defined as the last magnetic lens passed by the primary beam path. The final magnetic lens may be part of a combined magnetic-electrostatic lens. One or more electrostatic lenses may be disposed between the final magnetic lens and the object plane. The final magnetic lens may form at least a part of an objective lens of the particle optical arrangement.
According to a further embodiment, in the operating position, the differential pressure aperture is located between a final electrostatic lens of the particle optical arrangement and an object plane of the particle optical arrangement and/or between a principal plane of the final electrostatic lens and the object plane. The term “between a final electrostatic lens and the object plane” may be defined as being located between all electrodes of the final electrostatic lens on the one hand and the object plane on the other hand. The final electrostatic lens may be defined as the last electrostatic lens passed by the primary beam path. The final electrostatic lens may be part of a combined magnetic-electrostatic lens. One or more magnetic lenses may be disposed between the final electrostatic lens and the object plane.
According to a further embodiment, in the operating position, the differential pressure aperture is located between a final particle lens of the particle optical arrangement and an object plane of the particle optical arrangement and/or between a principal plane of the final particle lens and the object plane. The term “between a final particle lens and the object plane” may be defined as being located between all pole pieces and/or electrodes of the final particle lens on the one hand and the object plane on the other hand. The final particle lens may be a magnetic lens, an electrostatic lens and/or a combined magnetic-electrostatic lens.
According to a further embodiment, in the operating position, the differential pressure aperture is located between an objective lens of the particle optical arrangement and an object plane of the particle optical arrangement and/or between a principal plane of the objective lens and the object plane. The term “between the objective lens and the object plane” may be defined as being located between all pole pieces and/or electrodes of the objective lens on the one hand and the object plane on the other hand. The objective lens may be a magnetic lens, an electrostatic lens and/or a combined magnetic-electrostatic lens.
A distance between the object plane and the objective lens and/or a distance between the object plane and the principal plane of the objective lens may be greater than a distance between the object plane and the differential pressure aperture when the differential pressure module is in the operating position.
According to an embodiment, in the operating position, the differential pressure aperture is the only or a final differential pressure aperture through which the primary particle beam path passes. Through the differential pressure aperture, the primary particle beam path may enter into the interior of the specimen chamber.
According to a further embodiment, the differential pressure module comprises a guiding and/or supporting structure. The guiding and/or supporting structure may be configured to be engageable with a mating structure of the particle optical apparatus during the positioning of the differential pressure module. In other words, the positioning of the differential pressure module may bring the guiding and/or supporting structure into engagement with the mating structure.
The mating structure may be rigidly attached to the objective lens and/or attached to a component, which is rigidly connected to the objective lens. By way of example, the component is a housing, which at least partially accommodates the objective lens.
According to a further embodiment, the differential pressure module is selectively detachably coupled to the positioning arm. The particle optical apparatus may comprise a coupling system for coupling the differential pressure module to the positioning arm in a selectively detachable manner. The coupling system may be configured such that in the pressure-controlled interior of the specimen chamber (i.e. without venting the specimen chamber), the differential pressure module is selectively detachable and/or attachable to the positioning arm.
By way of example, the coupling system may comprise a coupling actuator, which is in signal communication with a controller of the particle optical apparatus. The controller may be configured to command the coupling actuator to selectively attach and/or detach the differential pressure module from the positioning arm.
According to an embodiment, the charged-particle optical apparatus further comprises a through-the-lens detector for detecting particles and/or radiation.
A through-the-lens detector may be defined herein as a detector, which is configured to detect emitted particles and/or radiation, which are emitted from the object, after the emitted particles and/or radiation have passed through a principal plane of a particle lens of the particle optical arrangement. The emitted particles may be object particles and/or primary particles. Additionally or alternatively, the through-the lens detector may be configured to detect radiation, such as cathodoluminescence radiation. The lens may be at least a portion of the objective lens. The through-the-lens particle detector may be configured to selectively detect primary particles and/or object particles.
According to a further embodiment, the charged-particle optical apparatus further comprises an aperture member. At least a portion of the aperture member may be conductive. At least a portion of the aperture member may be in the shape of a tapered tube. The tapered tube may taper towards the object. At least a portion of an inner peripheral surface and/or at least a portion of an outer peripheral surface of the aperture member may taper towards the object and/or may have a frustoconical shape. An object-side end portion of the aperture member may form at least a portion of the differential pressure aperture.
The differential pressure module may comprise a plurality of aperture members. For each of the aperture members, the respective aperture member may be in the shape of a tapered tube. Each of the aperture members may taper toward the object. The plurality of aperture members may form a plurality of vacuum zones.
According to a further embodiment, the particle optical apparatus comprises an objective lens. The advancing movement of the differential pressure module may represent a first path of the differential pressure module. At least a portion of the first path may be convex toward the objective lens. A starting point of the first path may be the non-operating position of the differential pressure module. The non-operating position may be defined as a position in which the differential pressure module is located at a distance from the primary particle beam path.
The differential pressure module may be brought into intersection with the primary particle beam path within the specimen chamber when following the first path.
According to a further embodiment, the first path is within a plane or is substantially within a plane. The plane may be oriented substantially parallel or oriented parallel to a direction of the primary particle beam path, wherein the direction of the primary beam path is measured at a location within the specimen chamber. Alternatively, the plane and the direction of the primary particle beam path may form an angle of less than 60 degrees, or less than 40 degrees, or less than 20 degrees, or less than 10 degrees, or less than 5 degrees.
According to a further embodiment, the first path is substantially linear over a length or linear over a length. The length over which the first path is linear or substantially linear may be at least 30 millimeters or at least 50 millimeters or at least 100 millimeters or at least 200 millimeters or at least 300 millimeters or at least 400 millimeters. The length over which the first path is substantially linear or linear may be less than 2000 millimeters or less than 1000 millimeters.
According to a further embodiment, the selective positioning of the differential pressure module includes performing a movement of the differential pressure module along a second path after completion of the first path. The second path may be a substantially linear path. The second path may be transverse or oblique or substantially perpendicular or perpendicular to the first path. An end point of the second path may be the operating position. At least a portion of the second path may be concave toward the positioning arm.
According to a further embodiment, the second path is substantially linear or linear over a length. The length over which the second path is substantially linear or linear may be least 1 millimeter or at least 3 millimeters or at least 5 millimeters or at least 10 millimeters or at least 20 millimeters. The length over which the second path is substantially linear or linear may be less than 200 millimeters or less than 100 millimeters.
According to a further embodiment, the length L1 over which the first path is linear or substantially linear divided by the length L2 over which the second path is linear or substantially linear (i.e. L1/L2) is greater than 5, or greater than 10, or greater than 30, or greater than 50, or greater than 100.
According to a further embodiment, the particle optical apparatus comprises a guide for guiding the track-guided movement of the positioning arm. The guide may include two mating guide members. The positioning arm may be movably connected to the guide to allow variation of an orientation of the positioning arm relative to each of the two mating guide members. The orientation of the positioning arm may be variable in a plane, which is substantially parallel or parallel to a direction of the primary particle beam path, wherein the direction of the primary particle beam path is measured at a location within the specimen chamber. The plane in which the orientation is variable may be parallel or substantially parallel to a plane in which the first path and/or the second path of the differential pressure module is located.
The first guide member may be configured as a rail, may form a guide track and/or may define a guiding path of the guide. The second guide member may be configured as a carriage and/or may be configured to be movable along the guiding path and/or the guide track. The positioning arm may be connected to at least one of the guide members of the guide at least in part via a resilient coupling and/or at least in part via an actuator. By way of example, the resilient coupling includes a spring.
According to a further embodiment, a degree of freedom of the positioning arm for performing at least a portion of the positioning of the differential pressure module is provided by the movable connection which movably connects the positioning arm to the guide to allow variation of the orientation of the positioning arm relative to each of the two mating guide members.
A portion of the present disclosure relates to the following embodiments:
Item 1: A charged particle optical apparatus, comprising: a particle optical arrangement, configured to define a primary particle beam path for inspecting an object; a specimen chamber configured to accommodate an object in a pressure-controlled interior of the specimen chamber during the inspection of the object; a differential pressure module having a differential pressure aperture; and a positioning arm being at least partially arranged in the specimen chamber and configured to selectively position the differential pressure module within the pressure-controlled interior of the specimen chamber into an operating position in which the primary particle beam path passes through the differential pressure aperture; wherein the selective positioning comprises an advancing movement of the differential pressure module directed toward the primary particle beam path, which is transmitted to the differential pressure module by a track-guided movement of the positioning arm.
Item 2: The charged particle optical apparatus of item 1, wherein a direction of the track-guided movement of the positioning arm and/or a direction of the advancing movement of the differential pressure module is oriented transverse or substantially perpendicular to a direction of the particle beam path measured at a location within the specimen chamber.
Item 3: The charged particle optical apparatus of item 1 or 2, wherein the advancing movement of the differential pressure module and/or the track-guided movement of the positioning arm is a substantially translational or a combined translational and rotational movement.
Item 4: The charged particle optical apparatus of any one of the preceding items, further comprising a guide for guiding the track-guided movement of the positioning arm; wherein a guiding path of the guide extends transverse or substantially perpendicular to a direction of the particle beam path, wherein the direction of the particle beam path is measured at a location within the specimen chamber; and/or wherein at least a portion of the guide is located outside the specimen chamber and/or in the surrounding atmosphere of the charged particle optical apparatus.
Item 5: A charged particle optical apparatus, comprising: a particle optical arrangement, configured to define a particle beam path for inspecting an object; a specimen chamber configured to accommodate an object in a pressure-controlled interior of the specimen chamber during the inspection of the object; a differential pressure module having a differential pressure aperture; a positioning arm being at least partially arranged in the specimen chamber and configured to selectively position the differential pressure module within the pressure-controlled interior of the specimen chamber into an operating position in which the particle beam path passes through the differential pressure aperture; wherein the selective positioning comprises an advancing movement of the differential pressure module directed toward the primary particle beam path.
Item 6: The charged particle optical apparatus of any one of the preceding items, wherein the advancing movement of the differential pressure module is a substantially translational or a combined translational and rotational movement; and/or wherein a direction of the advancing movement of the differential pressure module is oriented transverse or substantially perpendicular to a direction of the particle beam path measured at a location within the specimen chamber.
Item 7: The charged particle optical apparatus of any one of the preceding items, wherein the differential pressure module comprises a module-mounted detector for detecting particles and/or radiation; and/or wherein the charged-particle optical apparatus comprises a through-the-lens detector for detecting particles and/or radiation.
Item 8: The charged particle optical apparatus of item 7, wherein at least a portion of the differential pressure aperture is formed by a component of the module-mounted particle detector, which contributes to a generation of a detector signal in response to receiving particles and/or radiation.
Item 9: The charged particle optical apparatus of any one of the preceding items, wherein during the advancing movement of the differential pressure module, at least a portion of the positioning arm passes through at least a portion of an opening, which extends through a wall portion of the specimen chamber; and/or at least portion of a driving member of the particle optical apparatus, which is drivingly coupled to the positioning arm, passes through at least the portion of the opening.
Item 10: The charged-particle optical apparatus of any one of the preceding items, wherein the positioning of the differential pressure module comprises bringing the differential pressure module into abutment with an abutment portion of the charged particle optical apparatus; wherein in the operating position a conductive portion of the differential pressure module is electrically isolated from the abutment portion.
Item 11: The charged particle optical apparatus of any one of the preceding items, wherein the differential pressure module comprises a seal member for bringing the differential pressure module into sealing engagement during the positioning of the differential pressure module.
Item 12: The charged particle optical apparatus of any one of the preceding items, wherein the differential pressure module comprises an intermediate vacuum zone, wherein in the operating position of the differential pressure module, the particle beam path passes through the intermediate vacuum zone.
Item 13: The charged particle optical apparatus of item 12, wherein the intermediate vacuum zone comprises a vacuum port for evacuating the intermediate vacuum zone.
Item 14: The charged particle optical apparatus of any one of the preceding items, wherein the differential pressure module comprises two intermediate vacuum zones, wherein in the operating position of the differential pressure module, the particle beam path passes sequentially through the two intermediate vacuum zones; wherein each of the two intermediate vacuum zones comprises a vacuum port for evacuating the respective vacuum zone; wherein the charged particle optical apparatus comprises a branched vacuum line having two branch lines; wherein in the operating position, each of the two branch lines is connected in fluid communication with one of the two vacuum ports.
Item 15: The charged particle optical apparatus of any one of the preceding items, wherein during the advancing movement, the differential pressure module is brought into intersection with the primary particle beam path.
Item 16: The charged particle optical apparatus of any one of the preceding items, wherein in the operating position, the differential pressure aperture is located between a final magnetic lens of the particle optical arrangement and an object plane of the particle optical arrangement.
Item 17: The charged particle optical apparatus of any one of the preceding items, wherein in the operating position, the differential pressure aperture is located between a final electrostatic lens of the particle optical arrangement and an object plane of the particle optical arrangement.
Item 18: The charged particle optical apparatus of any one of the preceding items, wherein in the operating position, the differential pressure aperture is the only or a final differential pressure aperture through which the primary particle beam path passes.
Item 19: The charged particle optical apparatus of any one of the preceding items, wherein the differential pressure module comprises a guiding and/or supporting structure, which is configured to be engageable with a mating structure of the charged particle optical apparatus; wherein the positioning of the differential pressure module brings the guiding and/or supporting structure into engagement with the mating structure.
Item 20: The charged particle optical apparatus of any one of the preceding items, wherein a degree of freedom of the positioning arm for performing at least a portion of the positioning of the differential pressure module is provided by a guide clearance of a guide for guiding a track-guided movement of the positioning arm.
Item 21: The charged particle optical apparatus of any one of the preceding items, further comprising an objective lens; wherein the advancing movement of the differential pressure module represents a first path of the differential pressure module, wherein at least a portion of the first path is convex toward the objective lens.
Item 22: The charged particle optical apparatus of any one of the preceding items, wherein the advancing movement of the differential pressure module represents a first path of the differential pressure module, wherein the first path is within a plane, which is oriented substantially parallel to a direction of the primary particle beam path, wherein the direction of the primary beam path is measured at a location within the specimen chamber.
Item 23: The charged particle optical apparatus of any one of the preceding items, wherein the advancing movement of the differential pressure module represents a first path of the differential pressure module, which is substantially linear over a length of at least 30 millimeters, at least 50 millimeters or at least 100 millimeters.
Item 24: The charged particle optical apparatus of claim any one of items 21 to 23, wherein the positioning of the differential pressure module includes performing a movement of the differential pressure module along a second path after completion of the first path.
Item 25: The charged particle optical apparatus of item 24, wherein the second path is transverse or substantially perpendicular to the first path.
Item 26: The charged particle optical apparatus of item 24 or 25, wherein the second path is concave toward the positioning arm.
Item 27: The charged particle optical apparatus of any one of items 24 to 26, wherein the second path is a substantially linear path, wherein an end point of the second path is the operating position.
Item 28: The charged particle optical apparatus of any one of the preceding items, further comprising a guide for guiding the track-guided movement of the positioning arm, which comprises two mating guide members; wherein the positioning arm is connected by a movable connection to the guide so that an orientation of the positioning arm relative to each of the guide members is variable.
Item 29: The charged particle optical apparatus of item 28, wherein a degree of freedom of the positioning arm for performing at least a portion of the positioning of the differential pressure module is provided by the movable connection.